优化无线网络实时的人机接口

　　优化无线网络实时的人机接口

　　本文讨论了用于人机接口的不同无线接口，并评估了实时操作的不同功能。无线服务提供商，从硬实时标准如WirelessHART，基于ZigBee、Wi-Fi、蓝牙、网格，都有自己要扮演的角色非常不同的时序要求使用Atmel、Freescale半导体器件和模块和芯片。

　　有许多不同的无线技术可以提供到人接口的链接，给设计者很多机会优化应用程序的技术。

　　有些应用程序需要硬实时能力。监测一个关键的化学或核过程需要及时提供和显示信息，传感器和人类界面之间的联系至关重要。如果无线技术是可行的技术，这必须是一个明确的、低延迟的解决方案。没有这样的系统就有可能产生失控的情况，在那里，人类控制器对旧数据做出反应，使情况变得更糟。

　　Wireless versions of fieldbus protocols， such as WirelessHART， provide a way to deliver the real-time performance in a more flexible manner with wireless links. While it is based on the popular 2.4 GHz band， it also includes vital security and interference protection to ensure that every packet of information is delivered within a certain specified timeframe.

　　Many other industrial control applications do not require such time-critical links. Setting parameters on a screen can be done promptly for a human user but not require a hard real-time implementation. Robust yet flexible industrial protocols such as ZigBee， allow mesh networks to develop so that data can hop from one node to the next. This low-cost way of expanding a network creates challenges for implementing a real-time system， but is perfectly adequate for some human interface applications.